1. Field of the Invention
This invention relates generally to a fuel vapor control apparatus for use in a gasoline powered engine, such as an automobile engine, and more particularly to a fuel vapor control apparatus having valve means therein which can be kept closed by a biasing means to respective preset values even if the pressure of a gasoline vapor on the one side becomes larger than that of a canister vapor on the other side, and vice versa.
2. Description of the Prior Art
In general, a fuel vapor control apparatus is disposed between a gas-liquid separator attached to a gasoline tank and a canister connected to a carburetor via a pipe or suitable conduit.
In the conventional fuel vapor control apparatus, a valve member thereof usually constructed of a flexible material, such as, for example, rubber, and a thin notched groove is formed on the central portion of the valve member. A spring is usually provided for holding the valve member in a preselected position, and when the pressure of gasoline vapor at the gasoline tank side becomes higher than the preset load of the spring, as upon fully filling the gasoline tank, a projecting portion of the valve member is released from a seat portion and the pressure of the gasoline vapor is released into a canister. On the other hand, when the pressure of the gasoline vapor on the gasoline tank side approaches a vacuum condition, according to the consumption of the fuel therein, atmospheric pressure flows from the canister side to the gasoline tank side through the notched groove of the valve member. The pressure of the gasoline vapor is extremely increased when the gasoline tank is filled with gasoline, and it becomes hot in the summer time, when exposed to the heat, and since the valve member is made of a flexible rubber, the shape of the valve member is easily deformed after long utilization, such that the effectiveness of the sealability of the valve member is somewhat decreased or damaged, and the pressure of the gasoline tank side is therefore not maintained at a certain pressure. Also, the amount of gasoline vapor being released into the atmospheric air through the notched groove of the valve member becomes quite large.